Add base_isa setting for RISC-V

Author: romancardenas

CHANGELOG.md

@@ -11,6 +11,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/).
 - Adapt RISC-V specific codegen for `riscv-peripheral` v0.3.0 rework
 - Include `riscv-peripheral` peripherals in `Peripherals` struct
 - Ensure `__INTERRUPTS` are `#[no_mangle]` on Xtensa.
+- Add `base_isa` field to `riscv_config` to allow the `riscv_rt::core_interrupt`
+  macro to properly generate start trap assembly routines in vectored mode.
 
 ## [v0.36.1] - 2025-04-04
 

src/config/riscv.rs

@@ -1,3 +1,4 @@
+use log::warn;
 use proc_macro2::TokenStream;
 use quote::quote;
 
@@ -11,21 +12,38 @@ pub struct RiscvConfig {
     pub harts: Vec<RiscvEnumItem>,
     pub clint: Option<RiscvClintConfig>,
     pub plic: Option<RiscvPlicConfig>,
+    pub base_isa: Option<String>,
     pub mtvec_align: Option<usize>,
 }
 
 impl RiscvConfig {
     pub fn extra_build(&self) -> Option<TokenStream> {
-        self.mtvec_align.map(|align| {
-            quote! {
+        let mut res = vec![];
+        if let Some(base_isa) = self.base_isa.as_ref() {
+            let base_isa = base_isa.to_lowercase();
+            let rustcv_env = format!("cargo:rustc-env=RISCV_RT_BASE_ISA={base_isa}");
+            res.push(quote! {
+                // set environment variable RISCV_BASE_ISA to enforce correct base ISA.
+                println!(#rustcv_env);
+                println!("cargo:rerun-if-env-changed=RISCV_RT_BASE_ISA");
+            });
+        } else {
+            warn!("No base RISC-V ISA specified in settings file.");
+            warn!("If your target supports vectored mode, you must specify the base ISA.");
+            warn!("Otherwise, `riscv-rt` macros will not provide start trap routines to core interrupt handlers");
+        }
+        if let Some(align) = self.mtvec_align {
+            let rustcv_env = format!("cargo:rustc-env=RISCV_MTVEC_ALIGN={align}");
+            res.push(quote! {
                 // set environment variable RISCV_MTVEC_ALIGN enfoce correct byte alignment of interrupt vector.
-                println!(
-                    "cargo:rustc-env=RISCV_MTVEC_ALIGN={}",
-                    #align
-                );
+                println!(#rustcv_env);
                 println!("cargo:rerun-if-env-changed=RISCV_MTVEC_ALIGN");
-            }
-        })
+            });
+        }
+        match res.is_empty() {
+            true => None,
+            false => Some(quote! { #(#res)* }),
+        }
     }
 }
 
@@ -66,3 +84,15 @@ pub struct RiscvPlicConfig {
     pub core_interrupt: Option<String>,
     pub hart_id: Option<String>,
 }
+
+#[cfg_attr(feature = "serde", derive(serde::Deserialize))]
+pub enum RiscvBaseIsa {
+    #[serde(rename = "rv32i")]
+    Rv32I,
+    #[serde(rename = "rv32e")]
+    Rv32E,
+    #[serde(rename = "rv64i")]
+    Rv64I,
+    #[serde(rename = "rv64e")]
+    Rv64E,
+}